August LeetCoding Challenge Week 1: Day 6

find_all_array_dups.kt

class Solution {
    fun findDuplicates(nums: IntArray): List<Int> {
        fun twiceFound(uniques: MutableMap<Int, Int>, num: Int): MutableMap<Int, Int> {
            uniques.set(num, uniques.getOrPut(num){ 0 } + 1)
            return uniques
        }
        
        return nums.fold(mutableMapOf<Int, Int>(), { t, num -> twiceFound(t, num) }).toMap().filterValues{ it == 2 }.keys.toList()
        
    }
}